Dispersion in Natural Streams

The one-dimensional mathematical model of dispersion has been developed to account for the loss of dye due to decay and adsorption. This model predicts the time-concentration of the conservative pollutant in a stream where the lateral and vertical mixing of the pollutant are almost complete. A three-dimensional model of dispersion has been developed to compute pollutant concentration near the site of injection where the effects of lateral and vertical dispersion are important. Various empirical relationships to determine the longitudinal, lateral, and vertical dispersion coefficients in natural streams have been evaluated. The dimensionless longitudinal and vertical dispersion parameters have been found, which depend upon the Reynolds number only, while the lateral dispersion parameter depends on both the Reynolds number and the width-to-depth ratio of the stream.